1. Field of the Invention
The present invention generally relates to a disk drive, and more particularly to a servo system for a two-dimensional MEMS-based scanner, and a method for use with the servo system.
2. Description of the Related Art
A micro-electromechanical system (MEMS) can be utilized to generate nanometer-scale motion. While providing nanometer-scale, yet precise, positioning capability (e.g., 5 nm 1-sigma error), it is advantageous to build a capability to span micrometer-scale areas (e.g., 100 μm square range) in the X-Y plane. The larger span range enhances a scanner's application potential. A key application of such a scanner is in the area of atomic force microscopy (AFM)-based storage applications, such as in a system disclosed in Vettiger and G. Binning, “The Nanodrive Project,” Scientific American, pp. 47-53, January 2003, and PCT Publication No. WO 03/021127 A2.
In this system, a polymer media for recording information is supported by a scanner. Unlike a friction-free actuator system, such as the one found in a disk drive actuator, a MEMS-based scanner is dominated by strong stiffness-producing flexural elements that provide X-Y freedom for movement. However, the presence of significant stiffness in the actuator system is shown to produce steady position error with respect to a ramp-reference trajectory in scan mode, and also suboptimal seek motion to a target track prior to a scan motion.
Thus, a new servo architecture is needed to overcome the effect of resistance generated by a system of flexural elements (i.e., that are integral to a MEMS-based scanner) so that two-dimensional seek and track-following-scan performances are competitively achieved.